INTERNATIONAL SOCIETY FOR SOIL MECHANICS AND GEOTECHNICAL ENGINEERING This paper was downloaded from the Online Library of the International Society for Soil Mechanics and Geotechnical Engineering (ISSMGE). The library is available here: https://www.issmge.org/publications/online-library This is an open-access database that archives thousands of papers published under the Auspices of the ISSMGE and maintained by the Innovation and Development Committee of ISSMGE. Geotechnical Aspects of Design and Construction of the Mountain Cluster Olympic Facilities in Sochi Les aspects géotechniques des projets et de la construction des sites olympiques situés dans les pays montagneux autour de la ville Sotchi Fedorovsky V., Kurillo S., Kryuchkov S., Bobyr G., Djantimirov Kh., Iliyn S., Iovlev I., Kharlamov P., Rytov S., Skorokhodov A. Gersevanov Research Institute of Foundations and Underground Structures, Moscow, Russia, e-mail: [email protected] Kabantsev О. Moscow State Building Construction University, Moscow, Russia ABSTRACT: Construction of Olympic Facilities in Krasnaya Polyana, mountainous area near Sochi, was a real challenge to Russian geotechnical engineers for the lack of construction expertise in the area as compared to the Alpine mountain resorts with extensive record of such activities. The geotechnical challenges of construction in this mountainous cluster include, as follows: - assessment of deformation and strength parameters of eluvial and half-rock soils, including rubbly and gravely ones; - selection of reliable techniques to analyze stability of natural, transformed and strengthened slopes; - design of footings and counter-slide structures in order to ensure adequate safety accounting seismic actions and soil condition variations. The paper describes three case histories of Olympic construction projects within the mountainous cluster to illustrate how the above problems were solved. RÉSUMÉ : Les travaux de construction des bâtiments olympiques dans le massif montagneux de Krasnaya Polyana aux environs de Sotchi ont causé nombre de difficultés aux géotechniciens russes. Cela s'explique par le manque de l'expérience nécessaire en ce domaine dans cette région, contrairement au cas des stations de ski des Alpes, qui ont une plus ancienne et plus riche histoire de développement. Les problèmes géotechniques essentiels liés à la construction dans la dite région consistent en les points suivants: - évaluation des paramètres de déformabilité et de résistance des sols éluviaux et en partie rocheux, incluant des remblais rapportes ; - choix de méthodes pertinentes de calcul de stabilité des pentes naturelles, aménagées et renforcées; - conception de fondations et de structures installations para-glissements garantissant un niveau adéquat de stabilité, y compris pendant les séismes ou un changement d'état des sols. Dans cet article, on décrit trois études de cas relatifs à la construction des installations olympiques dans la région montagnarde pour illustrer comment ces problèmes ont été résolus. KEYWORDS: slope stability analyses, counter-slide structures. 1 INTRODUCTION quaternary, mostly formed from of argillite bedrocks. Closer to the surface gravelly clay-filled soils contain more clay and less Erection of Olympic facilities within the Sochi mountainous rock debris and gravel (Fig. 2). cluster (Krasnaya Polyana area) forced construction engineers, particularly geotechnical engineers, to face quite a few complicated problems due to tight deadlines, absence of expertise of such large-scale projects in the area, complicated geological conditions and seismicity. The situation dictated that the leading research organizations such as Gersevanov Research Institute of Foundations and Underground Structures would take part in the design of some facilities and structures along with expert evaluation of the project designs. The paper describes the main challenges of the above work on three Olympic projects and their respective solutions. 2. GEOLOGICAL ENVIROMENT The project (highway from Krasnaya Polyana to “Roza-Khutor” ski resort”, bobsleigh/luge track and a complex of ski-jumps) are allocated on the left-bank slope of Mzymta river and plateau expansion of Aigba ridge offspur at 950…1100 m altitudes with the valley bottom at 485…490 m. The terrain varies from gentle 5…15° slopes to steep 35…40° slopes. The Fig. 1. Outcropping argillite area is cut with streams – tributes to Mzymta. Such grain size composition complicates any tests to Geologically there are features from quaternary to determine soil deformation and, especially, strength parameters. underlying Jurassic deposits. The latter are mainly represented Therefore, pillar shear test was the main method along with by argillites, interlayered with sandstones and limestones. large-size sample (40 сm) direct shear test that required Stratified partly outcropping argillites occur below 10…20 m application of large-size test equipment. Additionally, pillar depths (Fig. 1). tests show the natural anisotropy of argillite properties due to its In terms of geotechnical engineering the main rocks are stratified structure. 3099 Proceedings of the 18th International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013 The road is constructed by cutting into the rock massif and sometimes by filling soil and by enlargement toward the lower slope. The objective was to select such strengthening solution for the upper and the lower slopes that would ensure the minimum value of kst, at least 1.15,for the main load (including 10 kPa load on the road proper) and 1.05 for the special (seismic) load. Where necessary, the upper slope was to be retained by anchors, inserted into the primary rock (argillite). In order to minimize the impact on the natural environment the upper slope retaining wall was made rather steep (60° versus the horizon) and 8…16 m high. In order to ensure adequate stiffness and strength of the slope plane 6..8 m long soil nails were proposed (Fig. 3). Fig. 2. Gravely clay soil At the initial stage gravely soil strength parameters were determined indirectly from results of crushing dry soil in a pebble mill (DalNIIS technique, 1989). Then the obtained parameters were corrected, because the natural slope stability analyses yielded faulty results (slope stability factor kst 1). Later the obtained experience made it possible to correlate the values of soil strength parameters with soil composition and state and thus to identify essential errors. Essential reduction of soil shear resistance after moistening was a specific feature of the terrain. The relief usually prevented long-term moistening by torrents and/or melting snow. However, soil strength parameters variation had to be taken into account in stability analysis as an action. Seismicity is yet another special action. Design seismicity of Fig. 3 Counter-landslide structures for the motor road. the terrain is reportedly from 8 to 9 points. In the analyses the Where the lower slope fill is insignificant, no extra measures seismic acceleration was generally assumed to be horizontal, were required. However, at some locations an angle-shaped but in some cases a more unfavorable direction had to be taken retaining wall, strengthened by a row of anchors, was to be into account i.e., at 30° versus the horizon. erected. However, it was insufficient for one of the cross- 3. KRASNAYA POLYANA – ROZA-KHUTOR ROAD sections, as the wall was supported by soft soil. It was proposed to replace the soil by broken stone fill or to strengthen it by Research and technological support of the motor road project grouting (рис. 3). was the authors’ first effort. Therefore, the basic analytical and Notably, application of anchors “neutralizes” both local design concepts were tested on this very project. landslides of the upper and lower slopes along with the global The first soil data was obtained by DalNIIS method (1989) ones, initiated above the road and ending below it. and initially looked dubious. It was especially so for gravel and The anchors were directly simulated in PLAXIS (with the pebble soils with clay fill, for which internal friction angle was account of transfer from 3D to 2D). In MVLM method the 23.8° and 26.6°, cohesion 13.6 kPa and 11.3 kPa respectively. plane, to which the anchors are fixed, is loaded to simulate For coarse-grain soils the values of were evidently stressed anchor action on the slope. Both methods demonstrated underestimated. This fact was proved by natural slope stability that the pulling force, applied to 2.5 m spaced anchors (along analysis. For some road cross sections the value of kst with the road), per 4 m along the slope is 40…45 tons. characteristic values of c and dropped down below 1.0 and Just a few words on seismic numeric simulation. Russian even below 0.8. standards recommend to apply proportional inertia forces to soil This was demonstrated after two stability analyses: by the weight with AK1 factor. Here A depends on the terrain seismic method of variable level of shear-strength mobilization intensity(А = 0.2 for magnitude 8), and K1 depends on allowable (MVLM), proposed by the authors (Fedorovsky, Kurillo, 1998, soil deformations. If a soil slope is viewed as a structure with 2001), and by finite elements analysis (Brinkgreve, Vermeer, limited (landslide) deformations then K1 = 1. If then the road 1998). Both methods MVLM and FEM (PLAXIS) yielded close subgrade is considered separately from the counter-slide kst values that were much lower than those obtained with the structures